Exposure method and exposure apparatus

ABSTRACT

While a current photosensitive substrate is being exposed on a substrate stage, the next photosensitive substrate for exposure is loaded on a temperature-adjustment plate for a predetermined time to remove a quantity of heat corresponding to a heat accumulation on the substrate stage during exposure. A substrate transporting system carries and loads the next photosensitive substrate, which has been cooled by the temperature-adjustment plate, onto the substrate stage. A pattern image of a mask is exposed and transferred onto the next photosensitive substrate through a projection optical system.

BACKGROUND OF THE INVENTION

[0001] This invention relates to an exposure apparatus used in aphotolithography process for manufacturing, for example, semiconductordevices, liquid crystal display devices, image pick-up devices,thin-film magnetic heads, and the like.

[0002] In manufacturing a semiconductor device or the like using aphotolithographic technique, a step-and-repeat type exposure apparatushas been conventionally used, in which a pattern of a photomask or areticle (referred to as a mask) is projected and exposed through aprojection optical system onto each shot area of a photosensitivesubstrate. Examples of the photosensitive substrate include asemiconductor wafer or a glass plate on which a photosensitizer (e.g.,photoresist) is applied.

[0003] A photosensitive substrate is loaded on a substrate stage andmoved within a two-dimensional plane, which is perpendicular to theoptical axis (Z direction) of the projection optical system. A pair ofmoving mirrors are fixed onto the substrate stage. A pair of laserinterferometers measure a distance from one of the moving mirrors,respectively, thereby detecting the coordinates of the substrate stagewithin the XY plane. A substrate stage control system drives thesubstrate stage by a predetermined amount in a stepwise manner withinthe coordinate system defined by the laser interferometers, so that eachshot area of the photosensitive substrate is brought into alignment withthe exposure field of the projection optical system.

[0004] A scanning type exposure apparatus has been developed, whichscans the mask and the photosensitive substrate in a synchronized mannerwith respect to the projection optical system. This type of exposureapparatus allows a pattern to be exposed onto a shot area that isbroader than the effective exposure field of the projection opticalsystem. The scanning type exposure apparatus can be of a collectiveexposure type or a step-and-scan type. In a collective type exposureapparatus, a pattern of a mask is projected and exposed onto the entirearea of a photosensitive substrate at a magnification ratio of one. In astep-and-scan type exposure apparatus, a mask pattern is exposed onto asingle shot area of a photosensitive substrate at a certain reductionratio, and when exposure of one shot area has been completed, the nextshot area is brought into the exposure field in the stepwise manner.

[0005] In any type of exposure apparatus, a mask and a photosensitivesubstrate must be precisely aligned to superpose the mask pattern onto apattern that has already been accurately formed on the photosensitivesubstrate. Generally, alignment sensors are provided in an exposureapparatus to detect a mask alignment mark that is formed on a mask and asubstrate alignment mark that is formed on a photosensitive substrate.Based on the detected position of the alignment marks, thephotosensitive substrate is aligned with the mask.

[0006] Alignment sensors used in the exposure apparatus include a TTL(through-the-lens) sensor system for detecting the position of thephotosensitive substrate through the projection optical system, a TTM(through-the-mask) sensor system for detecting a positional relationbetween the mask and the photosensitive substrate through the projectionoptical system and the mask, and an off-axis sensor system for directlymeasuring the position of the photosensitive substrate without using theprojection optical system. A reference mark is provided on the substratestage for calibrating the alignment sensors and detecting a distancebetween the center of the projected image of the off-axis alignmentsystem and the center of the projected image of the projection opticalsystem, which is a socalled base-line amount.

[0007] In general, a projection optical system used in an exposureapparatus has a large numerical aperture (NA) and a shallow focal depth.In order to transfer a minute pattern onto a photosensitive substratewith high resolution, a mechanism is required for bringing the surfaceof the photosensitive substrate into an image-forming plane of theprojection optical system. To this end, an oblique-incident typemultipoint autofocus (AF) system is provided to detect the focal point(i.e., the position along the optical axis) of a shot area on thephotosensitive substrate and an inclination of the surface of the shotarea. With the oblique-incident type autofocus system, a plurality ofmeasurement points are set within a shot area of the photosensitivesubstrate, and a plurality of slit images are obliquely projected to themeasurement points. The slit images reflected by the measurement pointsare formed on a photodetector. A focal point and an inclination of theshot area are determined from the image-forming positions of the slitimages on the photodetector. Based on the detection result of themultipoint AF system, autoleveling control for making the surface of ashot area parallel to the focal plane of the projection optical system,and autofocus control for bringing the focal position on the surface ofthe photosensitive substrate into the focal position of the projectionoptical system are performed. In this manner, each shot area is broughtinto an acceptable range of the focal plane of the projection opticalsystem.

[0008] As a mask pattern is repeatedly exposed onto respective shotareas of a photosensitive substrate, the temperature of thephotosensitive substrate rises because of the exposure energy of theillumination light. Moreover, when the photoresist layer formed on thephotosensitive substrate is exposed, a photochemical reaction is causedwithin the photoresist. If the photochemical reaction is an exothermicreaction, the temperature of the photosensitive substrate furtherincreases. Since the photosensitive substrate thermally contacts thesubstrate stage, heat generated in the photosensitive substrate istransferred to the substrate stage through conduction so that thephotosensitive substrate and the substrate stage are in thermalequilibrium.

[0009] A portion of the heat generated in the photosensitive substrateand transferred to the substrate stage is released in the airsurrounding the photosensitive substrate and the substrate stage.However, most of the heat is accumulated on the substrate stage throughthe repeated pattern exposure process. As a result, the temperature ofthe substrate stage rises. The temperature rise in the substrate stagecauses two major problems.

[0010] First, alignment between the mask and the photosensitivesubstrate is adversely affected. As has been mentioned above, varioustypes of alignment sensors are used in an exposure apparatus, which arecalibrated using a reference mark provided on the substrate stage. Thereference mark is used by the off-axis alignment system to control thebase-line amount. The reference mark is made of, for example, a quartzglass, on which a pattern is drawn by chromium and is fixed to the topsurface of the substrate stage. If the temperature of the substratestage changes, the reference mark slightly rotates.

[0011] Moving mirrors are also fixed to the substrate stage to measurethe X and Y coordinates of the substrate stage. When the temperature ofthe substrate stage rises, the position and the fixing angle of themoving mirrors change due to thermal deformation of the supportingmember of the moving mirrors. If the position or fixing angle of themoving mirror changes, the reference mark rotates relative to the movingmirror, which affects the base-line measurement. Deformation of thesupporting member of the moving mirror causes errors in theorthogonality of the coordinate system, as well as an offset amount.

[0012] Second, the autofocus function is adversely affected. An exposureapparatus is generally positioned in a chamber in which the atmospherictemperature is maintained constant by a temperature adjuster. If thetemperature of the substrate stage rises, the air surrounding thesubstrate stage wavers due to a temperature difference between theatmosphere and the substrate stage. An oblique incident AF detectionsystem emits a detection beam obliquely with respect to thephotosensitive substrate loaded on the substrate stage, and detects abeam reflected by the surface of the photosensitive substrate. If theair wavers around the substrate stage, the detection accuracy of the AFsystem drops due to the fluctuation of the air in the optical path ofthe detection beam. As a result, the autofocusing function of theapparatus deteriorates.

[0013] To cool the substrate stage, liquid cooling or air cooling may beconsidered. With liquid cooling, cooling tubes are attached to thesubstrate stage, through which a coolant is supplied. The substratestage, however, generally includes various mechanisms, such as X and Ystages for moving the photosensitive substrate within the XY plane, a Zstage for moving the photosensitive substrate in the Z direction toperform autofocus control, a tilting mechanism for tilting thesubstrate-loading plane to level the exposed surface of thephotosensitive substrate, and a loading/unloading mechanism fortransferring the photosensitive substrate between the substrate stageand a substrate transporting mechanism. If cooling tubes are attached tothe substrate stage, the structure of the substrate stage becomesfurther complicated. Moreover, whenever the substrate stage moves, thecooling tubes are trailed between the substrate stage and the pump forsupplying a coolant, which imposes a large amount of load on the stagedriving unit. On the other hand, the alternative air cooling method isinferior in cooling efficiency.

SUMMARY OF THE INVENTION

[0014] The present invention was conceived in view of the drawbacks inthe prior art, and it is an object of the invention to provide anexposure apparatus and an exposure method that can efficiently avoid atemperature rise in the substrate stage, even if pattern exposure isrepeated, without providing liquid cooling means or air cooling means.

[0015] This and other objects of the invention are achieved by removinga quantity of heat from a photosensitive substrate prior to loading thephotosensitive substrate onto the substrate stage. The quantity of heatcorresponds to a heat accumulation amount on the stage during anexposure of a single photosensitive substrate. A substrate stage isdefined as a device for loading and moving a photosensitive substrate inan exposure apparatus, and therefore, a substrate holder, movingmirrors, and other auxiliary components are regarded as a part of thesubstrate stage.

[0016] In one aspect of the invention, an exposure method is providedfor exposing a pattern of a mask onto a photosensitive substrate. Priorto loading the photosensitive substrate onto the substrate stage, aquantity of heat that corresponds to a heat quantity accumulated on thesubstrate stage during an exposure of one photosensitive substrate isremoved from the photosensitive substrate.

[0017] The heat quantity accumulated on the substrate stage duringexposure depends on the transmissivity of the mask, the reflectivity ofthe photosensitive substrate, the characteristic of the photosensitizer(photoresist), the number of shots made on one photosensitive substrate,the time required for exposing one photosensitive substrate, the timerequired for alignment, and other parameters. The heat quantity may bedetermined through calculation; however, it is more practical todetermine the heat quantity on an experimental basis.

[0018] For example, the heat quantity accumulated on the substrate stageduring exposure may be determined by loading a photosensitive substratethat has a temperature substantially equal to the substrate stagetemperature onto the substrate stage, and by detecting a temperaturerise of the substrate stage that occurs when a mask pattern is exposedonto the photosensitive substrate.

[0019] A temperature-adjustment plate may be used to remove thecorresponding heat quantity from the photosensitive substrate. Thetemperature-adjustment plate is cooled in advance to a temperaturesubstantially equal to a target temperature for the photosensitivesubstrate. The photosensitive substrate is loaded on thetemperature-adjustment plate so as to directly contact the plate for apredetermined period of time. The temperature-adjustment plate may becooled through the liquid cooling method using a coolant, or an electriccooling method using, for example, a Peltier element.

[0020] To determine the temperature of the temperature-adjustment plate,the temperature of the substrate stage is detected when a photosensitivesubstrate has been exposed. The temperature of thetemperature-adjustment plate is set based on the detected temperature ofthe substrate stage. The temperature of the substrate stage may bemeasured using a test substrate. Alternatively, in the case in which aplurality of photosensitive substrates are successively exposed in alot, the temperature of the substrate stage may be measured using thefirst photosensitive substrate of the lot.

[0021] Another way of removing the corresponding heat quantity from thephotosensitive substrate is to place the photosensitive substrate in aspace in which the atmospheric temperature has been set to a temperaturesubstantially equal to the target temperature for a predetermined periodof time. With this method, it is preferable to use a plate that is madeof a material with a high thermal conductivity to efficiently cool thephotosensitive substrate. The plate is positioned within the space inwhich the atmospheric temperature is set substantially equal to thetarget temperature of the photosensitive substrate. The photosensitivesubstrate is mounted on the plate, which is now in thermal equilibriumwith the atmosphere in the space, and efficiently cooled through directcontact between two solid bodies.

[0022] In another aspect of the invention, an exposure apparatus isprovided that comprises a substrate stage for supporting aphotosensitive substrate, a projection optical system for projecting apattern formed in a mask onto the photosensitive substrate, and atemperature-adjustment plate for cooling the photosensitive substrate toremove a quantity of heat from the photosensitive substrate prior toloading the photosensitive substrate onto the substrate stage. Thequantity of heat corresponds to a heat quantity that is accumulated onthe substrate stage during exposure of a photosensitive substrate.

[0023] A temperature sensor may be attached to the substrate stage tocontrol the temperature of the temperature-adjustment plate.

[0024] With this arrangement, it is not necessary to provide coolingtubes for supplying a coolant to the substrate stage. A photosensitivesubstrate is first brought into contact with the temperature-adjustmentplate to cool down, and then loaded on the substrate stage, whereby thetemperature of the substrate stage can be maintained substantiallyconstant based on heat exchange throughout the exposure process. Thismethod is much more effective than the air cooling method.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] These and other aspects and advantages of the present inventionwill be described in detail with reference to the accompanying drawings,in which:

[0026]FIG. 1 is a schematic block diagram of an exposure apparatusaccording to an embodiment of the invention;

[0027] FIGS. 2(a) and 2(b) illustrate the substrate stage used in theexposure apparatus shown in FIG. 1, in which FIG. 2(a) is a plan view,and FIG. 2(b) is a cross-sectional view taken along the A-A line of FIG.2(a);

[0028] FIGS. 3(a)-(c) illustrate an example of thetemperature-adjustment plate, in which FIG. 3(a) is a top view of thetemperature-adjustment plate, FIG. 3(b) is a cross-sectional view takenalong the B-B line of FIG. 3(a), and FIG. 3(c) is a bottom view;

[0029]FIG. 4 illustrates another example of the temperature-adjustmentplate

[0030]FIG. 5 is a flowchart showing a method of determining thetemperature of the temperature-adjustment plate according to anembodiment of the invention; and

[0031]FIG. 6 is a schematic diagram of an exposure apparatus accordingto another embodiment of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0032]FIG. 1 illustrates an exposure apparatus according to anembodiment of the invention. Illumination light emitted by a lightsource 1, such as a mercury-vapor lamp or excimer laser, passes throughillumination optical elements 3 a-3 c, while being reflected byreflective elements 2 a-2 c. The illumination optical elements 3 a-3 cshape the illumination light into a uniform illumination light beam. Themask 4, in which a pattern is formed, is illuminated by the shaped lightbeam with a uniform illuminance distribution. A pattern image of themask 4 is formed through the projection optical system 5 onto thephotosensitive substrate 6, which is coated with a photoresist. The maskpattern is thus transferred onto the photosensitive substrate 6. Thephotosensitive substrate 6 is held by the substrate holder 7 on thesubstrate stage 8, which is movable within a two-dimensional plane.

[0033] An alignment system 13 is provided in the vicinity of theprojection optical system 5 to detect an alignment mark that is formedon the photosensitive substrate 6 and a reference mark 14 (shown in FIG.2) that is formed on the substrate stage 8. An oblique incident AFsystem, which is composed of a light-transmitting system 16 and alight-receiving system 17, is also provided to detect a focal position(Z position) of the photosensitive substrate 6. The oblique incident AFsystem has a known structure, and is disclosed in, for example, Japanesepatent application laid-open no. 5-275313.

[0034] FIGS. 2(a) and 2(b) illustrate the substrate stage 8. FIG. 2(a)is a plan view, and FIG. 2(b) is a cross-sectional view taken along theA-A line in FIG. 2(a). The substrate stage 8 is equipped with anX-direction moving mirror 15X for detecting an X position of thesubstrate stage 8, and a Y-direction moving mirror 15Y for detecting a Yposition of the substrate stage 8. Laser beams are emitted by a pair ofinterferometers (not shown), respectively, toward the moving mirrors 15Xand 15Y. The interferometers determine the X and Y positions of thesubstrate stage 8 based on the laser beams reflected from the movingmirrors 15X and 15Y. A reference mark 14 is provided on the substratestage 8. A temperature sensor 12, which consists of a thermocouple orplatinum resistor, is fixed to the substrate holder 7 mounted on thesubstrate stage 8. An output of the temperature sensor 12 is connectedto an input of a controller 29. The temperature sensor 12 may be buriedin the top surface of the substrate holder 7 as indicated by the symbol12 a, or attached to the side face of the substrate holder 7 asindicated by the symbol 12 b.

[0035] Referring back to FIG. 1, the photosensitive substrate 9, whichis the next substrate to be exposed after the photosensitive substrate6, is loaded on the temperature-adjustment plate 20 at a waitingposition. The photosensitive substrate 9 is transferred between thewaiting position and the substrate holder 7 on the substrate stage 8through a substrate transporting device 11. The temperature of thetemperature-adjustment plate 20 is set to a target temperature T2 of thephotosensitive substrate. The target temperature T2 is lower than theatmospheric temperature T1 that surrounds the substrate stage 8 (i.e.,T2<T1). While the current photosensitive substrate 6 is held by thesubstrate holder 7 on the substrate stage 8, the next photosensitivesubstrate 9 is loaded on the temperature-adjustment plate 20, which hasbeen cooled to temperature T2. Since the next photosensitive substrate 9directly contacts the temperature-adjustment plate 20, heat exchangeoccurs between the photosensitive substrate 9 and thetemperature-adjustment plate 20, and the next photosensitive substrate 9reaches thermal equilibration with the temperature-adjustment plate 20.In this manner, the next photosensitive substrate 9 is cooled to T2before it is loaded on the substrate stage 8 for exposure.

[0036] FIGS. 3(a)-(c) show the detailed structure of an example of thetemperature-adjustment plate 20. FIG. 3(a) is a top view of thetemperature-adjustment plate 20, FIG. 3(b) is a cross-sectional viewtaken along the B-B line of FIG. 3(a), and FIG. 3(c) is a bottom view.

[0037] The temperature-adjustment plate 20 is made of a material with ahigh thermal conductivity, including, for example, an aluminum alloy orceramics. The temperature-adjustment plate 20 has a substrate liftingdevice 21 in the middle portion. The substrate lifting device 21 liftsthe photosensitive substrate 9 up and down to pass and receive thephotosensitive substrate 9 to and from the substrate transporting device11. The substrate lifting device 21 has three spindles 21 a-21 c thatfit into through-holes 22 a-22 c penetrating the temperature-adjustmentplate 20 from the top to the bottom thereof. Each of the spindles 21a-21 c has an adsorption hole at the tip, through which vacuumadsorption is applied to the photosensitive substrate 9. In other words,the spindles 21 a-21 c support the photosensitive substrate 9 throughvacuum adsorption, and in this state, they are vertically moved by adriving device 23, thereby transferring the photosensitive substrate 9to and from the substrate transporting device 11.

[0038] Vacuum holes 24 a-24 d are formed on the surface of thetemperature-adjustment plate 20. When the photosensitive substrate 9 isloaded onto the temperature-adjustment plate 20, the vacuum holes 24a-24 d are evacuated by an evacuation device 25 to firmly hold thephotosensitive substrate 9 on the temperature-adjustment plate 20.

[0039] A cooling tube 26 is laid on the bottom face of thetemperature-adjustment plate 20. A coolant, cooled to a predeterminedtemperature by a liquid conditioner 27, is supplied through the coolingtube 26 to remove the heat from the temperature-adjustment plate 20. Atemperature sensor 28 is buried in the temperature-adjustment plate 20consists of, for example, a thermocouple or platinum resistor. Thecontroller 29 regulates the liquid conditioner 27, while monitoring theoutput from the temperature sensor 28, so that the temperature of thetemperature-adjustment plate 20 is maintained at the preset targettemperature T2. The controller 29 also regulates the evacuation device25 and the driving device 23 for driving the substrate lifting device21.

[0040]FIG. 4 illustrates another example of the temperature-adjustmentplate 20. This temperature-adjustment plate 20 uses a Peltier element,instead of a coolant, to cool the photosensitive substrate. FIG. 4corresponds to FIG. 3(b), and the same elements are denoted by the samesymbols.

[0041] As shown in FIG. 4, a Peltier element 30 is attached to thebottom face of the temperature-adjustment plate 20 so that the coolingsurface of the Peltier element 30 directly contacts thetemperature-adjustment plate 20. The radiating surface of the Peltierelement 30 is equipped with a radiation fin 31. The Peltier element 30is connected to a power source 32. The controller 29 regulates the powersource voltage, while monitoring the output from the temperature sensor28, so that the temperature of the temperature-adjustment plate 20 ismaintained at the preset temperature T2.

[0042] The preset temperature T2 of the temperature-adjustment plate 20is determined in the following way. Assuming the atmospheric temperaturesurrounding the substrate stage 8 is set to T1, then the temperature T2for the temperature-adjustment plate 20 is defined as:

T2=T 1−ΔT

[0043] If exposure light generates thermal energy E(J) during anexposure of a photosensitive substrate, and if the photosensitivesubstrate has a volume V(cm³) and a heat capacity C(J/Km³), then thechange ΔT in the temperature is expressed as:

ΔT=E/(CV)

[0044] Because, however, a time taken for an exposure of aphotosensitive substrate varies depending on the type of the photoresistapplied to the photosensitive substrate, the thickness of thephotoresist film, and the reflectivity of the undercoat, the thermalenergy generated in each photosensitive substrate also varies.Therefore, the preset temperature T2 of the temperature-adjustment plate20 must be slightly adjusted. Moreover, not all the heat generated inthe photosensitive substrate is transmitted to the substrate stage, buta portion of the heat generated in the photosensitive substrate 6 isreleased into the atmosphere. For these reasons, it is more practical todetermine T2 based on actual measurement, rather than throughcalculation.

[0045]FIG. 5 is a flowchart showing an example of a method fordetermining the temperature T2 of the temperature-adjustment plate 20through actual measurement. This method utilizes the output from thetemperature sensor 12, which is fixed to the substrate holder 17. Instep S11, a photosensitive substrate 6, which has a temperature T1 equalto the temperature of the substrate stage 8, is loaded on the substratestage 8 and moved in a stepwise manner by the substrate stage 8 untilall the shot areas of the photosensitive substrate 6 are exposed. Instep S12, a temperature rise ΔTs in the substrate stage 8 is measuredafter the exposure of all the shot areas of the photosensitive substrate6. Because the substrate holder 7 and the substrate stage 8 are inthermal equilibrium with good mutual heat conduction, the controller 29can determine the temperature rise ΔTs in the substrate stage 8 from achange in the output of the temperature sensor 12 before and after theexposure of the photosensitive substrate 6.

[0046] In step S13, the controller 29 determines a heat quantity Qaccumulated on the substrate stage 8 during the exposure of thephotosensitive substrate 6, based on the temperature rise ΔTs of thesubstrate stage 8 detected in step S12. Then, the controller 29determines a necessary temperature change ΔTp required to cool thetemperature-adjustment plate 20 and remove the heat quantity Q from thesubsequent photosensitive substrates. The relation between thetemperature rise of the substrate stage 8 and the heat quantityaccumulated on the substrate stage 8, and the relation between thetemperature change in the photosensitive substrate and the heat quantitywere determined in advance by experimentation.

[0047] In step S14, the controller 29 controls the liquid conditioner 27(FIG. 3) or the power source (FIG. 4) to set the temperature of thetemperature-adjustment plate 20 to T2 which is expressed as:

T2 T1−ΔTp

[0048] The next photosensitive substrate is loaded on thetemperature-adjustment plate 20, which has been cooled to temperature T2according to the heat accumulation on the substrate stage 8, before itis loaded on the substrate stage 8. Thus, a quantity of heatcorresponding to the heat accumulation on the substrate stage 8 isremoved from the next photosensitive substrate 9 by thetemperature-adjustment plate 20 in advance, thereby preventing excessiveheat accumulation on the substrate stage 8 during exposure. In thismanner, a temperature rise in the substrate stage 8 can be preventedeven if a plurality of photosensitive substrates are successivelyexposed as long as a predetermined amount of heat is removed from thephotosensitive substrates before they are loaded on the substrate stage8. Since the temperature of the substrate stage 8 is maintained constantthroughout the exposure process, a drop in alignment accuracy betweenthe mask 4 and the photosensitive substrate 6 due to rotation ordeformation of the reference mark 14 formed on the substrate stage 8, ordeterioration in autofocusing accuracy due to fluctuation of the air canbe prevented.

[0049] The temperature adjustment plate 20 may remove a quantity of heatgreater than the heat quantity Q that is accumulated on the substratestage 8 during exposure of the photosensitive substrate as long as thephotosensitive substrate is prevented from being distorted by the heataccumulated on the substrate stage 8, and as long as the reference markis prevented from rotating due to the heat.

[0050] The temperature sensor 12 fixed to the substrate holder 7continuously detects the temperature of the substrate stage 8 andsupplies the detection result to the controller 29. When the controller29 detects a temperature change in the substrate stage 8 such that thereis still an unacceptable temperature rise at the end of the exposurestep of the current photosensitive substrate, the controller 29 canadjust the preset target temperature T2 of the temperature-adjustmentplate 20 so that the temperature of the substrate stage 8 returns to anacceptable temperature by the end of the exposure step of the nextphotosensitive substrate. For example, if the liquid coolingtemperature-adjustment plate 20 shown in FIG. 3 is used, the controller29 regulates the liquid conditioner 27 to change the temperature of thecoolant; if the Peltier element temperature-adjustment plate 20 is used,the controller 29 regulates the power source 32 to change the voltage.

[0051]FIG. 6 illustrates another example of the exposure apparatusaccording to the present invention In the previous example, atemperature-adjustment plate uses a coolant or a Peltier element to coolthe photosensitive substrate. In this example, the photosensitivesubstrate is cooled in a chamber in which the atmospheric temperature isset to the target temperature T2.

[0052] A mount plate 40 for mounting the next photosensitive substrate 9and a substrate transporting device 11 are positioned within the chamber41. The chamber 41 is filled with air cooled to the predetermined targettemperature T2. The mount plate 40 is made of a material with a highthermal conductivity including, for example, an aluminum alloy orceramics. The air is taken in by a vacuum ventilation fan 46 and cooledto the predetermined temperature by an air conditioner 47. The cooledair is supplied into the chamber 41 through a blast pipe 48. The airwithin the chamber 41 is exhausted through an exhaust pipe 49 outsidethe exposure apparatus. The mount plate 40 has a temperature sensor 50.A controller 51 monitors the output from the temperature sensor 50 andcontrols the air conditioner 47 so that the temperature of the chamber41 is maintained at the predetermined target temperature T2.

[0053] Similar to the previous example, the temperature sensor 12continuously detects the temperature of the substrate stage 8. When thecontroller 51 detects an unacceptable temperature increase in thesubstrate stage 8 at the end of the exposure step of the currentphotosensitive substrate, the controller 51 can adjust the predeterminedtarget temperature 12 of the air conditioner 47 so that the temperatureof the substrate stage 8 returns to an acceptable temperature by the endof the exposure step of the next photosensitive substrate.

[0054] Shutters 42, 44 are provided at the entrance and the exit of thechamber 41. The shutters 42 and 44 are opened and closed by shutterdriving devices 43 and 45, respectively, only when the photosensitivesubstrate is introduced into and sent out of the chamber 41, so thatleakage of the cooled air is suppressed as much as possible, and thetemperature of the chamber 41 is maintained constant.

[0055] While the current photosensitive substrate 6, which is held bythe substrate holder 7 on the substrate stage 8, is being exposed, thenext photosensitive substrate 9 is loaded on the mount plate 40 withinthe chamber 41 filled with the cooled air. The next photosensitivesubstrate 9 is cooled to a temperature T2 within the chamber 41 throughheat exchange with the cooled air and the mount plate 40, which has beencooled to temperature T2 by the cooled air. Then, the shutter 44 isopened by the driving device 45, and the substrate transporting device11 carries the next photosensitive substrate 9 to the substrate holder 7on the substrate stage 8.

[0056] With the exposure method and apparatus of the invention, heataccumulation on the substrate stage is efficiently avoided withoutproviding liquid cooling means or air cooling means. Accordingly,pattern exposure can be successively and repeatedly performed whilesuppressing a temperature rise in the substrate stage. Alignmentaccuracy between the mask and the photosensitive substrate andautofocusing accuracy can be maintained in the exposure apparatus.

[0057] While the invention has been described in connection with what ispresently considered to be the most practical and preferred embodiments,it is to be understood that the invention is not to be limited to thedisclosed embodiments, but on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims. For example, although the presentinvention has been described using an example of an exposure apparatusthat uses a mercury-vapor lamp or an excimer laser as a light source,the invention is not limited to this arrangement. The invention can beapplied to an X-ray exposure apparatus using an X-ray light source or anelectron beam exposure apparatus, which emits charged particles directlyonto a substrate without inserting a mask between the light source andthe substrate.

What is claimed is:
 1. An exposure method for exposing a mask patternonto a photosensitive substrate loaded on a substrate stage, comprisingthe step of removing a quantity of heat from the photosensitivesubstrate prior to loading the photosensitive substrate onto thesubstrate stage, the quantity of heat corresponding to a heat quantitythat is accumulated on the substrate stage during exposure of thesubstrate.
 2. An exposure method according to claim 1 , furthercomprising, prior to the removing step, the step of determining the heatquantity.
 3. An exposure method according to claim 2 , wherein the heatquantity determining step comprises: mounting a photosensitive substratehaving a temperature substantially equal to the temperature of thesubstrate stage onto the substrate stage; and detecting a temperaturerise in the substrate stage when the mask pattern has been exposed ontothe photosensitive substrate.
 4. An exposure method according to claim 3, wherein the heat quantity determining step further comprises the stepsof determining the heat quantity based on the detected temperature riseand determining a necessary temperature change required to remove theheat quantity from subsequent photosensitive substrates.
 5. An exposuremethod according to claim 2 , wherein the heat quantity determining stepcomprises calculating the heat quantity based on a thermal energy of anexposure light, a volume of the photosensitive substrate, and a heatcapacity of the photosensitive substrate.
 6. An exposure methodaccording to claim 1 , wherein the removing step comprises loading thephotosensitive substrate onto a temperature-adjustment plate that hasbeen cooled to a temperature substantially equal to a target temperaturefor a predetermined time.
 7. An exposure method according to claim 6 ,further comprising, prior to the loading step, the step of cooling thetemperature-adjustment plate to the target temperature.
 8. An exposuremethod according to claim 7 , wherein the cooling step comprises coolingthe temperature-adjustment plate with a liquid coolant.
 9. An exposuremethod according to claim 7 , wherein the cooling step comprises coolingthe temperature-adjustment plate with a Peltier element.
 10. An exposuremethod according to claim 6 , further comprising: detecting atemperature of the substrate stage upon completion of exposure of thephotosensitive substrate; and adjusting the temperature of thetemperature-adjustment plate based on the detected temperature.
 11. Anexposure method according to claim 6 , wherein thetemperature-adjustment plate includes a temperature sensor and a coolingtube disposed in contact with the temperature-adjustment plate, thecooling tube being coupled with a source of liquid conditioner, theremoving step further comprising regulating the liquid conditioner inaccordance with a signal from the temperature sensor to maintain thetemperature-adjustment plate at the predetermined temperature.
 12. Anexposure method according to claim 6 , wherein thetemperature-adjustment plate includes a temperature sensor and a Peltierelement coupled with a power source, the removing step flier comprisingregulating the power source in accordance with a signal from thetemperature sensor to maintain the temperature-adjustment plate at thepredetermined temperature.
 13. An exposure method according to claim 1 ,wherein the removing step comprises leaving the photosensitive substratein a space in which an atmospheric temperature has been setsubstantially equal to a target temperature for a predetermined time.14. An exposure method according to claim 13 , further comprising, priorto the leaving step, the step of cooling the space to the targettemperature.
 15. An exposure method according to claim 13 , wherein thespace includes a temperature sensor and an air conditioner, the methodfurther comprising monitoring output from the temperature sensor andcontrolling the air conditioner in accordance with the output from thetemperature sensor.
 16. An exposure method according to claim 13 ,further comprising: detecting a temperature of the substrate stage uponcompletion of exposure of the photosensitive substrate; and adjustingthe temperature of the space based on the detected temperature.
 17. Anexposure method according to claim 1 , further comprising, after theremoving step, transferring the photosensitive substrate from a waitingposition to the substrate stage, wherein the removing step is performedwhen the photosensitive substrate is in the waiting position.
 18. Anexposure apparatus comprising: a substrate stage that supports aphotosensitive substrate; a projection optical system disposed in avicinity of the substrate stage, the projection optical systemprojecting a pattern formed in a mask onto the photosensitive substrate;and a temperature-adjustment plate disposed remote from the substratestage, the temperature-adjustment plate cooling the photosensitivesubstrate by removing a quantity of heat from the photosensitivesubstrate prior to loading the photosensitive substrate onto thesubstrate stage, the quantity of heat corresponding to a heat quantitythat is accumulated on the substrate stage during exposure of thesubstrate.
 19. An exposure apparatus according to claim 18 , furthercomprising: a temperature sensor fixed to the substrate stage; and acontroller communicating with the temperature sensor and thetemperature-adjustment plate, the controller controlling the temperatureof the temperature-adjustment plate based on an output from thetemperature sensor.
 20. An exposure apparatus as claimed in claim 18 ,further comprising: a temperature sensor fixed to thetemperature-adjustment plate; and a controller communicating with thetemperature sensor and maintaining the temperature of thetemperature-adjustment plate based on an output from the temperaturesensor.
 21. An exposure apparatus according to claim 18 , wherein thetemperature-adjustment plate is formed of a material with a high thermalconductivity.
 22. An exposure apparatus according to claim 18 , whereinthe temperature-adjustment plate comprises: a temperature sensor buriedin the temperature-adjustment plate; a cooling tube secured to one sideof the adjustment plate and coupled with a source of liquid conditioner;and a controller communicating with the temperature sensor andcontrolling the liquid conditioner source, the controller regulating theliquid conditioner in accordance with an output from the temperaturesensor.
 23. An exposure apparatus according to claim 18 , wherein thetemperature-adjustment plate comprises: a temperature sensor buried inthe temperature-adjustment plate; a Peltier element secured to one sideof the adjustment plate and coupled with a power source; and acontroller communicating with the temperature sensor and controlling thepower source, the controller regulating the power source in accordancewith an output from the temperature sensor.
 24. An exposure methodcomprising the steps of: removing a quantity of heat from a substrate;loading the substrate from which said quantity of heat has been removedonto a substrate stage; and exposing the substrate loaded on thesubstrate stage to radiation flux.
 25. The exposure method according toclaim 24 , wherein said quantity of heat removed from the substratecorresponds to a quantity of heat that is accumulated on the substratestage during exposure of the substrate.
 26. An exposure apparatus forexposing a substrate into a prescribed pattern using radiation, theapparatus comprising: a substrate stage for supporting a substrate; anda heat remover for removing a quantity of heat from the substrate beforethe substrate is loaded on the substrate stage.
 27. The exposureapparatus according to claim 26 , wherein said quantity of heatcorresponds to a heat quantity that is accumulated on the substratestage during exposure of one substrate.